Evaluation of the off‐axis and on‐axis tensile creep behavior of glass‐fiber reinforced polymer unidirectional lamina

Abstract The off‐axis creep behavior of glass‐fiber reinforced polymer (GFRP) unidirectional lamina is crucial for engineering structural applications. A unified prediction model for time‐dependent off‐axis and on‐axis tensile creep strain in GFRP lamina is developed. The model, analogous in form to the one‐parameter plasticity model, accounts for off‐axis creep deformation separately for elastic and plastic response stages, incorporating a correction term to describe on‐axis creep deformation. The accuracy of the model is confirmed through tensile creep tests on unidirectional lamina at angles of 0, 15, 30, 45, 60, and 90 degrees. The model successfully predicts of creep deformation in the elastic and plastic response stages, respectively. The effects of creep stress, creep time, and off‐axis angle on the creep behavior are investigated. The optimal test angles for predicting off‐axis creep behavior using only two off‐axis angles' creep tests are analyzed. The dominant factors of creep behavior at various off‐axis angles are evaluated. The findings of the study include recommendations for lay‐up configuration and engineering applications of GFRP composites. Highlights A unified creep strain prediction model for GFRP lamina was developed. Creep strain was calculated separately in elastic and plastic response stages. The link between stress, time, angle and creep behavior was determined. The optimal test angles for predicting off‐axis creep behavior were evaluated.